Service stations which dispense gasoline and other fuels to automobiles typically utilize large tanks buried underground beneath such service stations from which the gasoline is dispensed. Such tanks require pumping systems which are also typically buried underground in isolated compartments, or sumps, near the storage tanks. In order to be able to inspect and service such pumping systems, the compartments in which they are housed are provided with large hatches, or lids, that are generally disposed at or about ground level, typically in the concrete surface near the gasoline pumps and parking lot of the service station. FIG. 1 shows a schematic cross-sectional view of an example upper portion of a perimeter portion of a prior art sump and access lid.
Referring to FIG. 1, the sump, shown generally at A, is formed from generally vertical walls 10 having a metal ring 12 disposed at the top. When initially installed, the sump is typically backfilled with gravel 14 capped by a layer 16 of concrete, which forms the surface upon which vehicles using the service station travel. In order to avoid interference with vehicles travelling on the concrete, the metal ring 12 is typically disposed at roughly the same elevation as the top surface 18 of the surrounding concrete. In order to protect the contents of the sump, a metal lid 20 sits generally on a recessed ledge 22 within the metal ring 12, thus placing the top 24 of the lid 20 roughly at the same elevation as the metal ring 12 and surrounding concrete 16. A drawback to such arrangement is that water on the surrounding concrete, such as rainwater, commonly enters the sump by way of the seam (not numbered) between the sump lid 20 and the metal ring 12. Such water can accumulate in the sump and lead to corrosion of the metal piping and other equipment located in the sump. Such corrosion creates a potential fuel release problem which presents a danger to persons nearby as well as a long term environmental concerns.
Accordingly, there exists a need for an improved sump design that allows human access while preventing water infiltration.